SAN FRANCISCO (CBS SF) — BART trains resumed normal service Monday night about an hour after a haze spotted in the Transbay Tube caused major BART delays while inspectors investigated, a BART spokeswoman said.

“Heavy haze” was first reported at 7:33 p.m. in the San Francisco-bound track of the tunnel, BART spokeswoman Alicia Trost said.

Trains went to single-track service, where only one train could enter the tunnel at a time, causing delays in both San Francisco- and East Bay-bound directions.

Crews went into the tunnel to inspect where the haze was coming from, but as of 8:05 p.m. reported that they had not found any evidence of the haze.

By 8:32 p.m. BART service resumed normally, Trost said.

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